Currently, secondary batteries represented by lithium-ion batteries or the like are widely used as power supplies for various mobile devices such as a mobile phone. In recent years, there is a great market demand to increase the capacity of power storage batteries for onboard use in electric automobiles and hybrid vehicles, large-size power storage use of back up power supplies of mobile phone base stations and the like, and middle-size power storage use of household back up power supplies, for example. Accordingly, it is expected that the opportunity to constantly use the secondary battery outdoors will increase. Therefore, there is a growing tendency to consider the temperature characteristics of the secondary battery as important.
In particular, at a low temperature, the characteristics of the lithium-ion battery are lowered and the deterioration progresses rapidly. The deterioration of the secondary battery is classified into a plurality of modes depending on conditions. For example, a lithium-ion battery is slowly deteriorated at a temperature equal to or higher than a room temperature (e.g., 15 C.° or more) and rapidly deteriorated due to precipitation of metal lithium at a temperature lower than the room temperature.
As a publicly known technique for monitoring the deterioration state of the secondary battery, for example, there is known a technique for estimating an amount of deterioration based on a square root of time, a temperature, and a state of charge (SOC) (e.g., Patent Document 1). Such a technique is configured to estimate a slow deterioration state at a temperature equal to or higher than a room temperature.
Patent Document 1: Japanese Patent Application Laid-open No. 2007-195312